Fully Time-domain Scanning of EM Near-Field Radiated by RF Circuits

Abstract—This paper deals with planar scanning technique of electromagnetic (EM) near-field (NF) emitted by electronic printed circuit boards (PCBs) fully in the time-domain (TD). The proposed EM scanning metrology is essentially based on the NF test bench available at the IRSEEM laboratory. It comprises motorized mechanical structures for moving the probe interconnected to electronic measurement instruments and controlled by a driver PC. The synoptic of the test bench is presented and technically examined. The characteristics of different elements constituting the measurement chain of the TD test bench understudy are described. The NF metrology developed is originally focused on the measurement of time-dependent magnetic field H(t) dedicated to the radiated emission electromagnetic compatibility (EMC) applications. An innovative calibration technique of the loop probe for detecting H(t) is established in order to ensure the post processing and extraction of the measured NF data. Then, validations were carried out via comparison with different simulations run with standard commercial tools. Mathematical analyses were also conducted for the improvement of the measurement post processing. To realize the mapping of time-dependent EM field components, a software interface edited with the graphical language LabVIEW was emulated to synchronize the probe displacement and the data acquisition. An UWB amplifier with average gain about 30 dB from DC to 300 MHz was designed and fabricated in order to decrease the measurement noise and to improve the quality of measured signals. As results of the study, TD NF mapping is demonstrated successfully by measuring the EM radiation emitted by electronic planar circuits. The technique developed is extremely useful in the field of EMC engineering for predicting the transient perturbations susceptible to degrade electronic functions in complex systems encountered usually for the automotive and aeronautic applications.